EP 0951642, which is incorporated herein by reference, discloses a processor unit. A commercial device with the technical principal described in the patent is known and comprises a processor unit in which a container preparation unit comprising several chambers is placed and in said container a sample of blood from a patient is arranged in order to be centrifuged. The process separates the blood into several layers in the first chamber during a centrifugation of the blood sample. The separated layers comprise at least a layer of red blood cells and a layer of plasma.
The plasma is transferred from the first chamber to the second by the movement of a piston that presses the layer of plasma through an opening into a channel that communicates with a second chamber. From the second chamber the plasma is further processed and treated in several chambers before the final product, a fibrin product or a Platelet Rich Fibrin (PRF) product, is extracted and applied in different ways i.e. in order to help the healing of a wound or stop bleeding during the operation of the patient.
The very important part of this process is to secure that the plasma is not contaminated with red blood cells. If this happens, it is due to the fact that red blood cells are transferred into chamber two from chamber one. In order to avoid this, a laser source is placed at the top wall of the container/preparation unit and is sending a signal through the channel that connects chamber one with chamber two. When the absorption of the laser light is changed, the transfer of the substance from chamber one to chamber two is stopped immediately, as this is a sign of red blood cells from the outer layer is contaminating the transferred plasma. Therefore, in this known device, there is a risk that the final product is contaminated with said red blood cells. Further, this way of controlling the process has the draw back that the volume of the transferred plasma is quite small compared to the amount of blood—120 ml—that is treated. Finally the amount of platelets is quite small when the product is used as a PRF product.
WO 98/30331 discloses a processor unit as described above. The movement of the piston of this processor unit is however regulated and controlled by a laser signal emitted from a source, said laser signal hits the surface of the piston. The laser signal is then reflected. The intensity of the reflected signal is registered and a control means stops the movement of the piston rod when a certain value is obtained. The system does not allow the piston to stop and move several times and as a consequence of that, the volume of the transferred plasma obtained by this arrangement is too small and thereby not satisfying.